Generation of gaseous mixtures for inflatable devices



g- 4, 1964 v. HEBENSTREIT 3,143,445

GENERATION OF GASEOUS MIXTURES FOR INFLATABLEDEVICES Filed Nov. 3. 1951 Fig.1

GAS INFLATABLE GENERATOR L DEWCE Y IZ ATTORNEY United States Patent 3,143,445 GENERATION 0F GASEOUS MIXTURES FOR INFLATABLE DEVICES Lester V. Hebenstreit, Bloomfield, N.J., assignor to Specialties Development Corporation, Belleville, N.J.,

a corporation of New Jersey Filed Nov. 3, 1961, Ser. No. 149,896 4 Claims. ((Zl. 149-1) The present invention relates to inflating inflatable devices, and, more particularly, to an improved charge for generating gaseous mixtures of carbon dioxide or the like and combustion products of propellants suitable for inflating such devices.

Heretofore, it has been proposed to inflate landing pads for helicopters and flotation equipment such as rafts, boats, escape ladders and the like with a mixture of carbon dioxide and the gases produced by propellants whereby the gases effected expansion of the carbon dioxide and the expanding carbon dioxide reduced the temperature of the gases and the mixture. However, under certain conditions of operation, the temperature of the mixture was not sufiiciently reduced to be safely withstood by the inflatable device or the pressure of the mixture was insufficient to fully inflate the device when cooled to ambient temperature.

Accordingly, an object of the present invention is to provide a charge for effectively inflating equipment without subjecting the equipment to excessive temperatures.

A further object is to accomplish the foregoing in a simple, practical, reliable and economical manner.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

In accordance with the present invention, it has been discovered that the foregoing objects can be generally accomplished by mixing the hot gaseous combustion products of pyrotechnic substances or propellants such as burning powders with a coolant comprising liquefied carbon dioxide and a material having a high heat of vaporization, such as ethyl alcohol for example. The hot gases heat and gasify the carbon dioxide to attain a desired pressure and the subsequent expansion of the carbon dioxide produces a cooling effect which reduces the temperature of the hot gases so that the mixture is at a temperature which the inflatable equipment can withstand. The temperature of the hot gases is further reduced and the pressure of the mixture is further increased by the alcohol or the like.

It is contemplated that a predetermined amount of heat is produced by the propellant for each pound of carbon dioxide used and a predetermined amount of alcohol is used for each 1000 B.t.u. of heat produced. These amounts may be varied for summertime or high ambient temperature operations (e.g. 20 F. to 125 F.) and for wintertime or low temperature operation (e.g. 20 F. to 80 F.) by using more carbon dioxide, more propellant and less alcohol in the wintertime than in the summertime, as will be explained hereinafter with reference to the specific examples of the present invention. Also, these amounts may be adjusted to compromise for summertime and wintertime operation to provide a charge operable within the temperature range of 20 F. to 125 F A preferred embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing, forming a part of the specification, wherein:

3,143,445 Patented Aug. 4., 1964 FIG. 1 is a schematic view of a system utilizing apparatus in accordance with the present invention for producing a gaseous mixture for inflating an inflatable device.

FIG. 2 is an enlarged longitudinal sectional view, partly in elevation, of apparatus for producing the gaseous mixture.

Referring now to the drawing in detail, a system is shown in FIG. 1 which comprises an inflatable device 10, a gas generator 11, and a conduit 12 for conducting a mixture of gases from the gas generator to the inflatable device.

The inflatable device 10 may be a bag of any desired shape and size used in connection with boats, rafts, rescue devices or helicopter landing pads.

The interior of the gas generator 11 for producing the mixture of gases is shown in FIG. 2. The gas generator comprises a container 15 for confining carbon dioxide; an outlet assembly 16 having the conduit 12 connected to its outlet 17; a pressure rupturable disc 13 for normally sealing the container to prevent discharge through the outlet; a hot gas generating chamber 19 including a charge 20 of propellant adjacent the outlet, an electrically actuated squib 21 for igniting the charge, and a passageway means 22 for conducting the hot gases from the chamber to the interior of the container 15 for admixture with the carbon dioxide; and a safety disc assembly 24 adapted to burst in the event an unsafe pressure is created within the container.

In operation, the squib 21 is actuated to ignite the charge 20, and the propellant generates hot gases which are admixed with the alcohol and the carbon dioxide to increase the pressure within the container 15 and burst the disc 18. This mixture is discharged through the outlet 17 and is conducted by the conduit 12 to the inflatable device 10 or other point of use. As this occurs, the hot gases increase the pressure of the carbon dioxide and vaporize the alcohol and the carbon dioxide upon expansion cools the hot gases by the Joule-Thomson effect which takes place when it is suddenly expanded from a high pressure to a much lower pressure, whereby the temperature of the mixture which enters the inflatable device is not too high to harm the device and the pressure of the gaseous mixture is adequate to fully inflate the device.

Numerous tests have indicated that, at ambient temperatures between -20 and F., the temperature of the gaseous mixture entering the bag can be maintained at between about 30 F. and about F. by varying the ratio of the number of B.t.u. produced for each pound of carbon dioxide. This ratio is higher at the lower ambient temperature than at the higher ambient temperatures. For example, at 20 F. about 159 B.t.u. may be ated by the propellant for each pound of carbon dioxide which is in excess of the heat theoretically required and to thereby take into account heat losses to atmosphere and work done in inflating the bag.

A propellant charge which has been found suitable is a potassium perchlorate type powder capable of producing about 1740 B.t.u. a pound. Thus, by varying the weight of the charge the desired number of B.t.u. to be produced can be predetermined within accurate limits.

Any suitable materials which remain in liquid state within the working temperature range and which have a high latent heat of vaporization may be utilized. Ethyl alcohol (synthetic) may be preferred because it is readily available and inexpensive, is readily mixed with the carbon dioxide in the container, and can be confined in the container together with the carbon dioxide. Also, the presence of ethyl alcohol has no harmful eflect on the components of the system.

The use of alcohol at high ambient temperature operation is particularly beneficial. At low ambient temperature operation, alcohol does "not reduce the temperature of the carbon dioxide to induce the formation of snow, but a smaller amount of alcohol can be used to control the temperature of'the gaseous mixture than at high temperature operation. For example, at -20 F. about 040 pound of alcohol is used for each 1000 B.t.u. produced by the charge, and at 125 F. about 0.66 pound of alcohol is used for each 1000 B.t.u. produced by the charge.

As specific examples of the present invention, a 56 cubic foot bag for a helicopter pad was inflated to a pressure of about three p.s.i.g. in less than four seconds by a hot gas generator container 11 having a volume of about 350 cubic inches and containing the following amounts of material:

Example 1 Working temperature range F 20 to 80 Carbon dioxide pounds 7.28 Pyrotechnic substance do 0.66 Ethyl alcohol do 0.46 Total weight of charge do 7.92 Bag temperature range F 4 to 136 Example ll Working temperature range F 20 to 125 Carbon dioxide pounds 6.89 Pyrotechnic substance do 0.57 Ethyl alcohol a do 0.66 Total weight of charge do 8.12 Bag temperature range F 36 to 155 I Example 111 Working temperature range F 20 to 125 Carbon dioxide pounds 7.33 Pyrotechnic substance do 0.67 Ethyl alcohol do 0.90 Total weight of charge do 8.90 Bag temperature range F 30 to 160 the bag. For example, such'compounds are ammonia,

ethane, propylene and nitrous oxide. Ammonia can be employed in systems where its dangerously toxic and corrosive nature and high water solubility can be tolerated.

From the foregoing description, it will be seen that the present invention provides a simple, practical and economical charge for inflating inflatable devices.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

I claim:

1. A charge for producing a mixture of cool gases under low pressure consisting essentially of about 0.57 to about 0.67 pound of a hot gas-generating pyrotechnic substance, said pyrotechnic substance being one which produces about 992 to about 1165 B.t.u.. when said 0.57 to 0.67 pound of substance is ignited, an expandable fluid coolant isolated from and surrounding said substance, said coolantconsistin'g essentially of about 6.89 to about 7 .33 pounds of carbon dioxideand about 0.46 to about 0.90 pound of ethyl alcohol, said charge bei ng a total weight of about 7 .92 to about 8.90 pounds, said pyrotechnic substance and said isolated coolant being of an arrangement to cause said isolated coolant to admix with hot gases to be generated by said pyrotechnic substance when said pyrotechnic substance is ignited.

2. A charge according to claim 1, consisting essentially of about 0.66 pound of said pyrotechnic substance which produces about 1148 B.t.u. when ignited, about 7.28 pounds of said coolant, and about 0.46 pound of ethyl alcohol, said charge being a total weight of about 7.92

pounds.

3. A charge according to claim 1, consisting essentially of about 057 pound of said pyrotechnic substance which produces about 992 B.t.u. when ignited, about 6.89 pounds References Cited in the file of this patent UNITED STATES PATENTS 164,818 Duc June 22, 1875 923,801 Bargar June 8, 1909 1,008,646 Kassner Nov. 14, 1911 1,328,088 Lutz Jan. 13, 1920 1,339,431 Backhaus May 11, 1920 1,659,384 Thomas Feb. 14, 1928 2,028,651 Dagnall et al Jan. 21, 1936 2,478,958 Wheeler et al Aug. 16, 1949 2,687,541 1 Banninster Aug. 31, 1954 2,886,424 Hyslop May 12, 1959 2,989,381 Musser June 20, 1961 3,024,595 Helvenston et al Mar. 13, 1962 3,049,872 Johnson et a1. Aug. 21, 1962 FOREIGN PATENTS 13,492 Australia 4 Jan. 1'5, 1929 

1. A CHARGE FOR PRODUCING A MIXTURE OF COOL GASES UNDER LOW PRESSURE CONSISTING ESSENTIALLY OF ABOUT 0.57 TO ABOUT 0.67 POUNT OF A HOT GA-GENERATING PYROTECHNIC SUBSTANCE, SAID PYROTECHNIC SUBSTANCE BEING ONE WHICH PRODUCES ABOUT 992 TO ABOUT 1165 B.T.U. WHEN SAID 0.57 TO 0.67 POUND OF SUBSTANCE IS IGNITED, AN EXPANDABLE FLUID COOLANT ISOLATED FROM AND SURROUNDING SAID SUBSTANCE, SAID COOLANT CONSISTING ESSENTIALLY OF ABOUT 6.89 TO ABOUT 7.33 POUNDS OF CARBON DIOXIDE AND ABOUT 0.46 TO ABOUT 0.90 POUND OF ETHYL ALCOHOL, SAID CHARGE BEING A TOTAL WEIGHT OF ABOUT 7.92 TO ABOUT 8.90 POUNDS, SAID PYROTECHNIC SUBSTANCE AND SAID ISOLATED COOLANT BEING OF AN ARRANGEMENT TO CAUSE SAID ISOLATED COOLANT TO ADMIX WITH HOT GASES TO BE GENERATED BY SAID PYROTECHNIC SUBSTANCE WHEN SAID PYROTECHNIC SUBSTANCE IS IGNITED. 